Converting char buffer to BInary

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Hi,

I have done RSA ENCRYPTION using C program and got the encrypted message in character buffer. I need to send this encrypted message to a different system in a binary format. So far googled it and trying hard to find the answer, all are in vain.

Anyone pls suggest how to convert a character buffer to a character Binary array?

CODE SNIPPET:

void EncrCardPin(char *pin,char *encpin)
 {
     unsigned char* encrypted = (unsigned char *) malloc(256);


    int bufSize;
    char *pubname=publkey.pem;

    FILE *keyfile = NULL;
    RSA* rsa= NULL;
    FILE *test = NULL;

    test=fopen("test.txt");

    printf(Opening the puclic key file: [%s]\n;,pubname);
    keyfile = fopen(pubname);

    if (!keyfile)
    {
        printf("error occured while reading public key file");

    }
    printf("Reading the public key block from: [%s] \npubname);
    rsa =   PEM_read_RSA_PUBKEY(keyfile, NULL, NULL, NULL);

    if (rsa == NULL)
    {
        printf("Badness has occured! Did not read  public key file\n";);

    }
    else
    {
        printf("Opened public key file OK!\n");
    }
    printf("Encrypting the message [%s] using public key \n",pin);
    bufSize = RSA_public_encrypt(strlen(pin), (unsigned char *) pin, encrypted, rsa, RSA_PKCS1_PADDING);
    if (bufSize == -1)
    {
        printf("Badness has occured! encryption failed\n");
        RSA_free(rsa);

    }
    else
    {
        printf("Encrypted the message OK! \n");
        //memcpy(encrypted,encpin,1500);
        sprintf(encpin,%s,encrypted);
        fprintf(test,%s,encpin);
        
    }
    RSA_free(rsa);
    fclose(keyfile);
    fclose(test);
 }

******************************************************

Hi,

I have added the RSA_size(rsa) command and free( encrypted). But I am getting coredump on RSA_size(rsa).

Also I want to calculate the size of encrypted variable. But I tried with strlen(), I am getting different length value while execution. 'Bufsize' value always = 256 but the encrypted character value always varies with different values. It should be 256, I hope ...Please suggest.

I need to copy this encrypted value into another character buffer and I have to send as a packet via TCP / IP. I am confused while copying to character buffer.

Need some idea on the above.

Thanks.

Posted 10-Apr-11 23:56pm

rprtech

Updated 12-Apr-11 22:39pm

v5

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3 solutions

Solution 1

If you want to write binary data to a file, you must open it with "wb" argument (write binary). And since your output file will contain binary data, I suggest not to name it ".txt".

Then, you shouldn't use fprintf but fwrite:

FILE* test = NULL;
...
test = fopen("test.bin", "wb");
...
fwrite(buffer, 1, numberOfBytesToWrite, test);
...

If you want to open and read your binary file, use fopen(..., "rb") and fread(...).

Posted 11-Apr-11 0:09am

Olivier Levrey

Solution 3

rprtech wrote:
printf("Reading the public key block from: [%s] \npubname);

I see a mistake in the above line.

rprtech wrote:
Anyone pls suggest how to convert a character buffer to a character Binary array?

You simply don't need that (as a character buffer already is a binary array or, in other words, a binary array is a superset of a character buffer - if you mean ASCII buffer -).

Posted 11-Apr-11 0:15am

CPallini

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markkuk · Accepted Answer · 2011-04-11T00:13:00

Solution 2

The array encrypted is already a binary array. No conversion is needed. Your code has some other errors that need fixing. For example, you forgot to free() the encrypted array, and its size should be RSA_size(rsa) instead of being fixed to 256 bytes.

Posted 11-Apr-11 0:13am

markkuk